MESOSCALE DISCUSSION 1630
   NWS STORM PREDICTION CENTER NORMAN OK
   0601 PM CDT MON JUL 20 2009
   
   AREAS AFFECTED...PARTS OF ERN WY...WRN  AND CNTRL NEB
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 606...
   
   VALID 202301Z - 210030Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 606
   CONTINUES.
   
   THE MAIN MID/UPPER FORCING FOR UPWARD VERTICAL MOTION IN THE EXIT
   REGION OF A STRONG NORTHWESTERLY HIGH LEVEL JET...AND AHEAD OF THE
   DIGGING UPPER TROUGH AXIS...HAS SHIFTED EAST SOUTHEAST OF THE
   NORTHERN ROCKIES INTO THE NORTH CENTRAL HIGH PLAINS.  IN ITS WAKE
   ...NORTHERLY LOW-LEVEL WINDS AND INCREASINGLY SUBSIDENT MID-LEVEL
   FLOW MAY SUPPRESS FURTHER STRONG CONVECTIVE DEVELOPMENT ACROSS MUCH
   OF WYOMING.  A POSSIBLE EXCEPTION COULD BE ACROSS THE HIGHER TERRAIN
   NEAR CHEYENNE...WHERE THE RISK FOR VIGOROUS STORMS MAY PERSIST
   ANOTHER COUPLE OF HOURS.  OTHERWISE...THE CONVECTION OF MOST
   SIGNIFICANCE IS NOW EVOLVING ACROSS THE IMPERIAL NEB AREA...WHERE AN
   UPSCALE EVOLUTION OF SUPERCELLS INTO A GROWING STORM CLUSTER APPEARS
   UNDERWAY.  THIS ACTIVITY IS EXPECTED TO SPREAD ACROSS THE REMAINDER
   OF SOUTHWEST NEBRASKA INTO NORTHWEST KANSAS THROUGH 00-01Z...WHERE
   STEEP LAPSE RATES...MODERATE POTENTIAL INSTABILITY AND MODERATELY
   STRONG SHEAR BENEATH 30-40 KT 500 MB FLOW WILL SUPPORT THE
   CONTINUING RISK FOR LARGE HAIL.  DAMAGING WIND POTENTIAL LIKELY WILL
   ALSO INCREASE AS CONSOLIDATING COLD POOLS STRENGTHEN AND ADVANCE
   SOUTHEASTWARD.
   
   ..KERR.. 07/20/2009
   
   
   ATTN...WFO...ICT...GID...LBF...DDC...UNR...GLD...BOU...CYS...
   RIW...
   
   LAT...LON   43650696 44160503 43240262 41850042 40979905 40219865
               39449866 39039909 38870035 39120164 39880201 40660280
               41140420 41500525 42210608 43650696